Backflow preventer



Oct. 6, 1953 Filed Nov. 7, 1944 T. A. GLASS 2,654,388

BACKFLOW PREVENTER 3 Sheets-Sheet 1 T. A. GLASS BACKFLOW PREVENTER 3Sheets-Sheet 2 Oct. 6, 1953 Filed Nov. 7, 1944 #la E 1". A. GLAssBACKFLOW PREVENTER Oct. 6, 1953 3 Sheets-Sheet 3 Filed Nov. 7, 1944 IQ MFigs. 6 and 7 show the device in full open and in nearly closedpositions, respectively.

Figs. 8 and 9 show modified forms of the disk and ring,

Fig. 10 shows a modified valve.

In Fig. 1 is shown my preferred form of back flow preventer, including amain valve body ill thru which fluid passes from the inlet II to theoutlet [2, past a check valve which is closed during periods of no flowand whenever the outlet pressure equals or exceeds the inlet pressure.In keeping with the suggested requirements the relief valve !6 is of aCapacity to discharge up to one-fifth of the normal flow in case ofleakage into the main valve body. This relief valve !6 is acted upon byopposed pressures of the inlet and outlet sides of the main valve.Referring par ticularly to Figure 4, while it seems from the figure thatthe diaphragms 6!) and 65 are the same size, there is a very slightdifference and the diaphragm '55 hasa slightly greater area. Hence,since the outlet pressure is exerted upon a larger area than is theinlet pressure, the relief valve IG will be opened to the atmospherewhenever the two opposing pressures are equal in head or in pounds persquare inch. The dierence in area is very slight, for example, in the 4"size the diaphragm 60 which is subjected to the inlet pressure, would be4" in diameter and the outlet diaphragm 65, subjected to the outletpressure, Would normally be l in diameter.

The body o has an arched cover ll and may carry a plug !8 having aninserted rubber bumper :9 acting as a stop for the valve !5 when fullyopen. The cored passage 20 in the body forms the middle portion of thecentral zone. The central zone extends from the inner seat 25 to theouter seat 26 and includes a waste pipe controlled by the valve egoverned by the pressures in the inlet zone. The inlet zone is up to theinner seat 25 and the outlet zone includes the piping beyond outer seat26 including the chamber 21 of body n and the outlet l2. Detachablysecured to the body I a, as by bolts 21, is a bronze casting 22 havingan annular recess 23 forming the inlet section of the central zonebounded by an inner seat 25 and an outer seat 26 preferably lying in asingle plane, although the outer seat may extend further into thechamber 21 of the main valve body !5, it being important that the outerseat 26 be closed before the inner seat 25 and opened later so that thecentral zone is first closed to the outlet water and then closed to theinlet water and that the central zone be opened to the inlet waterbefore being put in communication with the outlet water which may benon-potable, as when the consumer has an emergency tank filled from anearby stream.

While the bracket 29 might extend from the body, it is more convenientto form this as an extension of the casting 22 so that the entireassembly may be removed as a unit when the top cover H is off. The hinge30 is in the form of a yoke and having widely spaced arms 3| looselyreceiving a mounting pin 32 carrying a weight' 33 to maintain a pressuredrop in excess of two pounds to insure that the differential reliefvalve shall stay closed when either or both of the seats are uncovered,that is, that the relief valve be closed at all times when there is aflow in the normal direction thru the main valve. The extra weightmounting pin 32 may be kept in place in any conventional manner.

The valve closure [5 may be of any convenient type and is shown in Fig.1 as compose of a s 4 36 held by two clamp plates 31 and 38 inengagement with a rubber facing 40 engaging both of the annular seats 25and 26, and a flexible member 4! which might be of laminated metal, butis preferably of a sheet membrane. The facing 48 is secured to the ring44 as by the clamp ring 45 and the membrane 4! is similarly secured tothe ring 44 by the clamp ring 46. Since both AD and 41 are flexible, thering 44, which is thicker axially than the disk, has a slight movementaxially of the common axis of the disk, ring, and closure. The ring andthe disk have engaging shoulders 48 and 49 to limit the outward movementof the disk when the closure starts to open and one or the other ofthese closure members carries a small annular rubber seal 50 te preventforeign particles getting into the space between the shoulders 48 and 49to lessen the relative movement of the disk and ring. The axial pin 5!is threaded at both ends, as shown, but might be integral with eitherthe clamp plate 31 or the nut 52 which engages the Washer 53 holding inplace the yoke of the hinge 30 and the sleeve 54.

Considering now the differential relief valve !6, the body is ofstandard Construction having a pair of valves 56 and 51 on a commonstern 58 which, however, extends thru flexible sheet membranes 53 onopposite sides of the body and is secured at one end? to a diaphragm 60acted upon by the inlet pressure transmitted by pipe 61, leading from aconnection 62 near the inlet flange. The other end of the valve stern 58is secured to a diaphragm 65 acted upon by the outlet pressuretransmitted by a pipe 65 leading from a connection 61 near the outletfiange of the main valve body I 0. A pipe 10 much larger than pipes 6Iand 56, leads from the cored passage 20 to the relief valve inlet 'H sothat when the relief valves are open the central zone fluid may bedischarged thru the relief valve outlet M, preferably thru a pipe 15having thei-ein a flow responsive element 16 controlling a visualindicator 11 for a slight flow and an audible indicator 18 for a largerflow so as to notify the attendant of abnormal conditions.

It is advisable to have the relief valve outlet '14 at a level wellabove the main line so that the central zone is always filled withwater, if that be the fluid passing the main valve. By this the?draining of the central zone every time there is no flow is avoided andalso the relief valve is protected from sand and sediment sifting intoit as would occur with the relief valve located beneath the main valve.It is advisable to coat the bodies of the valves with porcelain enamelto avoid corrosion and incrustation.

As a Construction refinement to increase the ease of inspection andrepairs, the seat and central zone casting 22, together with the diskand ring assembly !5, can be removed from the valve body thru its opentop. This can be done by removing the valve body cover i? and theoutside cap screws 2l that hold the seat and central zone casting. A newgasket 24 of suitable sheet material between the casting and the valvebody will seal the joint against leakage when the seat casting issecured in place With the holding cap screws. To facilitate the removalof the disk assembly !5 without removing the seat casting 22, the hingepin can be withdrawn thru the hole 8! opposite the pin. The diskassembly can then be lifted free of the valve body for inspection orreplacement.

In Fig. 10 there are two spring pressed valves 84 and 85 having a commonstem 83 and, there-'- fore. actingas a unit. The rehe! valve.- Ii& asbefore: is; governed' by' opposing inlet and outlet pressure& thru:pipes: BB" and 81 communicating with the inlet; chamber- 88: andthe-outlet: chamber 83,. respectivelyg. The central zone 90: in. thistype is: cylindrical and vents. thru the. relief: valve ta by the.waste. pipe m.

The closure is` much more' efiioient than if the rubbe: facingi 40 werebacked: by' a: solid member, as the latter would require too great adrop ina outletpressure before the' valve could open. Assuming a 4 size,seats of 4% and 6% diameter; and an inlet. pressure ot 60 pounds, it`would: necessitate the momentary fall of the outlet pressureto 20.pounds before the flow could start from statio pressure. 'I-lhisnaturallywould prevent the use of faucets lo'- cated higher than 46 feetabove the main line. But by making: the closure in two pieces with thedisk 4 inches in diameter; it would necessitate the momentary fall ofoutlet pressure to- 4 1 7 pounds to rai'se the disk off its seat. Whenthe outerseat only is closed and' the: outlet pres'- sure is i'l pounds,the force holding the ring to its seat is only about 200 pounds and theforce holding the disk ofi' its seat is about 196 paund& The resultantforce then, that isholding the ring to its seat is a force; of but 3pounds. A further drop in pressure of a few ounceswill force the ringfrom its seat and flow will' start and these few ounces will continue tohold the close assembly justfree of the seats.

We will now consider the operation of the back flow preventer; startingwith the position shown in, Fig. 'T which illustrates the mechanism asit Would' appear just after the demand for water had ceased in thehouse, factory or other consumer's property. With the cessation of flow,the pressure in the body ID* starts to. built up. The closure !5,aid'ed' by extra weight 33', tends to turn about its pivot 80' onbracket 29' and close flow of water from the body w across the centralzone. The seat 26 is closed prior to the closing of the seat of theinlet' pipe, hence the inlet is stillopento t-hecentral zone. Thechamber 20 and valve s are filled, but the relief valve is not yetwasting as the pressure in the body n has not quite risen to the pointwhere the greater exposed area of the membrane 65 is able to overcomethe lesser area of membrane 60 where the pressure is substantially theinlet pressure, as the flow is so slight. Almost immediately after thefirst closing of the valve |5 the body pressure reaches the necessarypoint to overcome the somewhat higher pressure at the left of the valveHi so the relief valves 56 and 51 open, as shown in Fig. 7, and this isfollowed by the complete closure of the val-ve !5, both of the concentrcseats being now engaged by their respective facings, so that no waterflows from the inlet or from the outlet. The central zone is then opento atmospheric pressure, as it always is when there is no flow thru thesystem. This incidentally takes care of any possible leakage from thebody and insures that such leakage cannot pass to the main.

Although the relief valve 16 is open to atmosphere during all periods ofno flow, it closes promptly when a faucet is opened in the consumer'spremises, and remains closed during all of the flow. The demand causes aslight drop in pressure in the body ID. This is immediately refiected atchamber 65, so that pressure on the opposite side closes the reliefvalve. At the same time the pressure of the Water on the inlet sidearthe clos..u i-eli:` opensrthiedisk ssemblrin part. water now flowing'from; the.. inletto the; central zone build ng un. pressure therein. asthe water cannoteape as long asgthe valve t&- is closed. The portionothegdi-sk assembly l-inri n irom the: first or: seatmores to its: back,position. and in: thepreierredconstruction. contact& fimlywiththeshoulder. ot the, cute:: ring of: closure !5, This closure nowopens: to flow fromvinl t to duhet; The extra; weight; &3; is so locatedto came ia. higherrpressure. differentiali at: the; &nale atao/nich theclosurehangssfrom its pivot; 8.& when the'.- nate of flow: of: the wateris: low; Il'he :lehet valve consequently eld: c osed until ter' hdemand; to waterithe consumers .premisemas ceamdiasjtstecplaned.,

tsapparent from theabovethat no, back flow can occur normatmas a greateroutl t pres ur would' merely hold. the closne all` the. tighter againsti s two-seats and: hold the, relief'valve. in wideiopen position. bindenertraordinaryz condi tions' nem tor exannleas. would. occur ita; foreign, body were. caught between; the closure and the; seats, the relief;val ve would open. wide.. and its chamber would' continuously waste thrupipe 15,; This, howevem would be ndicated, first by the lamp; H' and;then; by' the bell ta; bringing p omnt attention..

Ina the: modified forms shown. in figures& and 9 are shown slight;modifications of the facing material; and the dexible -nemlarane Iheform of Figo e is; somewhat preferred over that of F 8; and; shows, thebody: seats. 25 and' 25; touchi-n inserted' facings Me; of semizhardrubher com: position facing material. In Eig; 8: the; facing material;ao is bronzeand; in this figure: the flexible material ist of themetallio. type as shown at 42th This inconveniently silver sol'dered as;at &2: at: the end of' the bend; so as to provide the necessarymovement..

Lolaim::

1.. !k guidcd, closure. plate. for a back flow pre: Mentor.. consisting:of a di k. a ring: cnaxal: with the disk.: and hatme: a should r d engcment iherewith; a racin formen of; a. sin le piece engaging both thedisk and the ring, a flexible sheet carrying the ring and engaging thedisk on the side opposite the facing, clamping means for securingtogether the facing, disk, ring, and sheet, and means for guiding theclosure plate.

2. In a back flow preventer, a body having a plurality of concentricports, means carried by the body for closing the ports in sequenceincluding a single closure, and means tending t hold the closure inport-closing position with constantly lessenng force as the closureopens under urge of the inlet pressure at the central port.

3; A back flow prevention valve for insertion between a potable Waterintake and a discharge pipe which might be connected to non-potablewater, comprising avvalve body or casing having a major chamber and acommunicatng passage forming part of a central zone, a removablemultiple valve seat and closure detachably secured within the bodyhaving concentric seats so that the inner seat is the sole portadmitting intake water and the space between the two seats is the solecommunication between the major chamber and said part of the centralzone, said body having an opening of such size as to receive theremovable valve seat and closure for withdrawal, a cover for saidopening, said closure being hinged and including a ring to engage theouter seat, a disk to engag the inner seat and flexible means connectingthe ring and the disk so they Will normallymove together but the diskwill have lost motion so as to move with respect to the ring when theinlet pressure exceeds the pressure in the central zone, said bodyhaving an inlet member communicating with the intake and having anopening therein for transfer of pressure and also having an outletmember leading from the major chamber and having an opening therein fortransfer of pressure.

4. In a valve comprising a body having a pair of concentric, adjacentports, a closure unit mounted adjacent said ports and movable towardsaid ports for closing one of said ports and subsequently closing theother port, said closure unit eomprising a portion of relatively largearea exposed to pressure within the body for closing the first mentionedport, a portion of smaller area for closing the second mentioned port,said last mentioned area being protected from pressure within the bodyby the closing of the one port, said one port being the outer of the twoconcentrio ports, and flexible means joining the portions wherebypressure within the body greater than the pressure in the other or innerport exerted on the closure unit to move it toward the ports will causethe portion of larger area to move into port closing position in advanceof the portion of smaller area, as the portion of smaller area is movedaway from port closing position by the pressure in the body of thevalve.

5. The device of claim 4 in which th closure unit comprises a disk ofrelatively large area on the seat side and a ring of relatively smallerarea on the seat side surrounding the disk and movable relative thereto.

6. In a back flow preventer a valve body having an inlet, an outlet, achamber communicating with the inlet and the outlet and a wastedischarge passage communicating with the chamber in spaced concentricrelaton to the inlet, an inner seat within the chamber surroundin theinlet, a disk within the chamber and movable into engagement with theinner seat to interrupt communication between the chamber and the inletwhen the pressure within the chamber exceeds the pressure' within thein1et,' an outer seat within the chamber surrounding the waste dischargepassage in spaced concentric relation to the inner seat, a ringsurrounding the disk and movable therewth for engaging the outer seatand interrupting the passage of fluid from the chamber into the wastepassage, and means carried by the disk and connected to the ring forsupporting said ring for movement relative to the disk 7. The device ofclaim 6 in which the disk and ring contacting faces of the inner andouter seats lie in the same plane, and the disk and ring are pivoted tomove as a unit progressively and sequentially into closing relation withthe inner and outer seats respectively when fluid pressure in thechamber equals or exceeds the pressure of fiuid in the inlet.

8. The device of claim 6 in which the area of the disk exceeds the areaof the ring whereby when the inlet and waste discharge passage areclosed th pressure of the disk against its seat exceeds the pressure ofthe ring against its seat.

THOMAS A. GLASS.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 968,'794 Peare Aug. 30, 1910 1,044,623 Bailey Nov. 19, 19121,1G5,991 Miller Aug. 4, 1914 1,198,128 Hills Sept. 12, 1916 1,648,486Larsen Nov. 8, 1927 1,668,456 Jennings May 1, 1928 1,693,842 Grimes Dec.4, 1928 1,765,422 Grimth June 24, 1930 2,068,833 White et al Jan. 26,1937 2,162,779 Lentwiler June 20, 1939 2,303,808 Wolcott Dec. 1, 1942FOREIGN PATENTS Number Country Date ?47,081 France V Mar. 21, 1933

